The present invention relates to a semiconductor device and a manufacturing method thereof, and in particular, to a semiconductor device having a metal resistive element and a manufacturing method thereof.
Microcontroller products and oscillators have been structured separately from each other before, but in recent years, oscillators are embedded in microcontroller chips in order to reduce layout areas and cost, etc. In order to embed an oscillator in a microcontroller chip, it is needed to output stable oscillating frequencies under any environment (voltage, temperature), and it is required to achieve, for example, 40 MHz±1% as a target accuracy in a high-speed OCO (On Chip Oscillator) circuit of a microcontroller product.
In order to achieve the aforementioned target accuracy, it is desirable to adopt titanium nitride (TiN) in a resistive element for a constant current generation circuit in a high-speed OCO circuit that is an analog circuit of an oscillator. One reason why TiN is adopted is that, because a so-called piezo-resistance effect is not generated in TiN, a variation in resistance values, occurring due to the stress resulting from a piezo-resistance effect, is small. The accuracy in oscillating frequencies can be enhanced with a variation in resistance values being reduced. Another reason for this is that, because the temperature dependence of a resistance value in a circuit using TiN is appropriate in a silicon process, TiN is suitable for being used as a so-called barrier metal covering the upper and lower surfaces of wiring. Resistive elements using TiN are disclosed, for example, in Japanese Unexamined Patent Publication No. 2011-155192 (Patent Document 1) and Japanese Unexamined Patent Publication No. 2004-303908 (Patent Document 2).